The article "Surface damage on stainless steel and molybdenum electrodes caused by electrical breakdown in high vacuum" by M. K. Sinha, Yee-Gee Ku and Randall P. Johnson in J. Appl. Phys., Vol. 52, No. 2, February 1981, pp. 699.congruent.705, shows and describes the behavior of pure metal electrodes (for example, steel or molybdenum) upon connection in a high vacuum. As illustrated in FIG. 2 of this publication, bubble nucleation leads to cracking and consequent destruction of the surface.
DE-OS No. 3224644 relates to a cathode for gas lasers made from three metal carbide layers, such as tantalum or niobium, and a method for its manufacture.
According to DE-PS No. 3148570 or EP-A No. 0081081, an improvement of the discharge properties of a catalytic gas laser can be achieved by adding low-ionizing molecules to the gas.
In "Elektrische Kontake und ihre Werkstoffe", Spring Verlag, 1984, pp. 48 et seq., the emission of electrons from metals by field and thermal emission is discussed. This reference explains that in metallic solids the electrons are freely movable, which in accordance with the so-called Fermi statistics can be explained through incompletely occupied energy bands. Further, this reference discloses the galvanic production of contact materials in energy technology (pp. 171 et seq.), the production of solid solutions by sintering (pp. 185 et seq.), and the coating of materials with a carrier layer by plating (pp. 279 et seq.). The method of powder metallurgy is selected when heterogeneous materials made of two or more components cannot be joined to each other by smelting because of their total or also slight solubility in the solid as well as in the liquid state.
These contact materials, in the manner of ionic plating, applied by chemical vacuum deposition (CVD), laser chemical vacuum deposition (LCVD), and physical vacuum deposition (PVD), have to date found no application in discharge physics because the physical processes have only limited similarity. The arc time constant in the former case is about 10 msec and the current density is about 10.sup.6 A/cm.sup.2. This differs by powers of 10 from corresponding values in discharge physics, where the spark time is in the nanosecond range and the current density is about 10.sup.2 A/cm.sup.2.
In gas lasers, such as the excimer or CO.sub.2 lasers, as well as in laser amplifiers and switches, such as spark gaps, with triggering and discharge critical gas mixtures, for example, high CO.sub.2 or O.sub.2 content, as well as all those with high gas pressures, fast catalyzers and large power densities with a high power supply and pulsed operation, the requirements with respect to electrical discharge are especially high. During the time interval for preionization and primary discharge essentially controlled by the pulse timing, shape and peak power, the laser mode, lifetime, and reproducbility are controlled for the discharge operation as such.